There presently exist many situations which involve supporting a plurality of slide mounted units in a stacked arrangement where it is desirous in the trade to allow only a single unit at a time to be withdrawn or extended from the stack. An example of this involves the use of heavy slide mounted disk drives, typical in the computer industry, which are maintained usually in free standing, roll about cabinets. Often during their use, it is necessary to extend a disk drive from the cabinet for replacement or servicing etc. If a second disk drive is thereafter extended there exist the dangerous possibility that the cabinet may tip over due to the extension of the second as a result of a change in the center of gravity of the cabinet.